1. Field of the Invention
The present invention relates to a shape measurement apparatus for measuring a spherical shape of an object to be examined, particularly, a shape measurement apparatus suitable for measuring a spherical shape of a cornea of an eye to be examined, a spherical shape of a contact lens and the like.
2. Description of Related Art
A corneal shape measurement apparatus for measuring a spherical shape of a cornea of an eye to be examined (meridional radius of curvatures of a steepest meridian and a flattest meridian, and an axial angle in the direction of the steepest or flattest meridian) is used for measuring a spherical shape (a base curve) of a contact lens (radius of curvatures on a concave surface side) in addition to the corneal shape measurement. In this case, a convex surface is measured at the time of the measurement of the corneal shape, while a concave surface is measured at the time of that of the base curve of the contact lens. In order to comply with both of the measurements, a measurement target symmetrical to the measurement optical axis (a target which has an annular shape having the measurement optical axis at its center or four targets which are vertically and horizontally symmetrical to the measurement optical axis) is generally used.
However, the conventional apparatus does not determine whether the measured spherical surface of the object is convex or concave. Therefore, an examiner need manage measurement data and it is bothersome for the examiner. For example, as is different from the measurement of the corneal shape having a convex surface, in the case of that of the base curve of the contact lens having a concave surface, the examiner makes a memo in printed data that the data is as to the contact lens (the concave surface measurement data). In addition, in the case of the measurement of a base curve of a contact lens having an astigmatic axis depending on a corneal shape of an examinee, the direction of its principal meridian (AXIS: an axial angle) need be reversed laterally, and the examiner performs reverse by manual calculation.
Further, in the case of the measurement of the base curve of the contact lens, as is different from that of the corneal shape, a back-surface reflection (a reflection from a convex surface side at the time of the concave surface shape measurement) exists, and it results in a problem of influencing on measurement accuracy.
An object of the invention is to overcome the problems described above and to provide a shape measurement apparatus which is capable of saving time and effort of an examiner and improving measurement accuracy.
To achieve the objects and in accordance with the purpose of the present invention, a shape measurement apparatus for measuring a spherical shape of an object to be examined comprises a measurement unit where a first projection optical system projects first targets for measurement onto a spherical surface to be measured of an object to be examined, a first detection optical system detects images of the projected first targets and a calculation unit obtains a shape of the spherical surface based on the detected images of the first targets, an output unit which outputs the obtained shape of the spherical surface, a mode setting unit which sets any one of a first measurement mode for measuring a convex shape and a second measurement mode for measuring a concave shape and a condition setting unit which sets at least one of a measurement condition and an output condition based on a mode setting result, the measurement condition and the output condition in the first measurement mode being different from the measurement condition and the output condition in the second measurement mode.
In another embodiment of the present invention, a shape measurement apparatus for measuring a spherical shape of an object to be examined comprises a measurement unit where a first projection optical system projects first targets for measurement onto a spherical surface to be measured of an object to be examined, a first detection optical system detects images of the projected first targets and a calculation unit obtains a shape of the spherical surface based on the detected images of the first targets, a second projection optical system which projects second targets of a configuration or shape pattern not symmetric about a point with respect to a measurement reference axis onto the spherical surface, a second detection optical system which detects images of the projected second targets, and a judging unit which judges whether the spherical surface is a convex shape or a concave shape based on a pattern of the detected images of the second targets.
Additional objects and advantages of the invention are set forth in the description which follows, are obvious from the description, or may be learned by practicing the invention. The objects and advantages of the invention may be realized and attained by the apparatus for determining corneal ablation data and the corneal surgery apparatus in the claims.